1. Field of Invention
The present invention relates generally to the field of wireless communication and data networks. More particularly, in one exemplary aspect, the present invention is directed to methods and apparatus for adjusting signal reception based on estimations of network load.
2. Description of Related Technology
In telecommunications networks, “orthogonality” refers to systems, processes, signaling, effects, etc. which exhibit desirable exclusionary properties. Orthogonal properties are heavily leveraged in multiple access communication schemes. Consider an aggregate signal composed of several orthogonal constituent signals. Ideally, a receiver can extract a desired signal from the aggregate signal, and reject the other orthogonal constituent signals. In this example, each of the orthogonal constituent signals is removable “interference”.
For example, CDMA (Code Division Multiple Access) based systems utilize a complex series of orthogonal “spreading codes” to distinguish between each data and control channel. A CDMA signal can be separated into its constituent channels, ideally without interference between the constituent channels (i.e., inter-channel interference or ICI).
In contrast to unwanted orthogonal signaling, true noise is “non-orthogonal” and does not exhibit simple exclusionary properties. For example, true noise includes elements such as nearby interfering systems, thermal noise, transmission effects, etc. Unlike orthogonal signaling, true noise is largely unpredictable and cannot be removed. Generally, true noise must be corrected using error correction techniques, or rendered insignificant to the transmitted signal power.
In typical wireless reception, an RF frontend “conditions” and converts a received RF waveform to a digital representation for subsequent demodulation and/or processing. Most designs for RF frontends implement signal conditioning stages before demodulation and/or processing stages. Also, RF frontends are typically constructed around fixed point arithmetic for cost and simplicity reasons (i.e., a fixed number of digits are used for operations).
Unfortunately, practical design constraints can create artifacts in normal operation. For example, in low noise environments, unwanted orthogonal signals can have much higher transmission power than the desired signal. These unwanted orthogonal signals will dominate the signal conditioning operations. As described in greater detail subsequently herein, such conditions can occur when a mobile device is very close to a sparsely unoccupied base station (or femtocell). Once the unwanted orthogonal signals (such as pilot channels, broadcast channels, etc.) have been removed, the desired signal is significantly under-powered, which can create quantization error effects in fixed point circuitry. Quantization errors can lead to much higher bit error rates (BERs).
Therefore, improved methods and apparatus are needed for handling scenarios where large differences are observed between known interference and desired signals. Such improved methods and apparatus should ideally facilitate successful decoding of signals, regardless of the current cellular conditions. Specifically, new solutions are needed for preserving cellular network performance, in low-noise, high-interference rejection environments.
Furthermore, it is additionally recognized that corresponding improvements are needed to existing hardware. Ideally, implementation of the aforementioned improved methods and apparatus should not require substantial changes to extant transceiver hardware or software. The non-ideal behaviors of hardware-specific implementations should be accounted for in signal conditioning, demodulation, post-processing, etc.